CIS with a 3.2 or 3.4. Is it worth it?

[Michel J]

Originally, I had posted this on the Engine Rebuild Forum, but, I thought I would solicit from this one as well since it much more active.


Here is what I have put together so far.

- 78 3.0 euro core motor with the larger ports heads
- heads have been rebuilt, with new valves, valve job, and with stronger HD springs from Dougherty Racing Cams
-heads are single plug and will be staying this way
-camshaft have been ground to 964 profile and rockers arms rebushed and re-profiled(Dougherty Racing Cams)
-new rocker shafts
-oil pressure chain tensioners
-longer stroke 74.4mm crankshaft with special oil groove modification machined in #5 journal (for better oiling)
-3.2 rods rebushed and balanced with ARP bolts
-set of 95mm (3.2L, 9.5 CR ) JE pistons and used (but good) honed 3.0 Nicasil cylinders
-SSI heat exchangers
-Magnaflow muffler

I plan on running CIS for a while and possibly going to EFI down the road in a year or two. We`ll see. This 3.2 seemed like a plan I could live with, but, now I am wondering if it would be worth my while and $ to sell the 95mm p and cs set and go for the 98mm setup. I am thinking this would set me back about $1200 after selling my 95mm set on the PP site or on ebay.

This engine will be running on 91 octane fuel and used mainly on the street with about 3 or 4 DE events a year. It will be installed in a 76 911S Targa. The original engine will be kept for smog checks. ( I rebuilt that one last year after missing a shift at SOW. Ouch!!$$ )

Given the above information, what would you do if you were me? Is is worth the extra $ and effort to sell the 95 for the 98s and gain 7% or so more power?

Thanks for your input.

Michel

[bigchillcar]

i think this is a question ultimately best answered by you. personally, i'd find it hard to get 'too excited' over an increase of 7% unless i was basically getting it for next to nothing..a grand to me is money i'd rather have in hand i think. i'd rather get the exact same thing for free by losing weight to the tune of 7%..or more.
ryan

[Bobboloo]

The 78'/79' induction and exhaust will limit your gains in the jump from 3.2 to 3.4 so in reality it's more than an extra $1200 if you want the full benifit of the increase to 3.4Ls. That being said it will still work and you will have a lot of punch below 4k RPMs. You just won't be able to realize the big HP potential of having 3.4Ls.

The 3.4 conversion will make for a fun street car but considering that you like to track the car it might be better to spend the extra cash on improvements to the induction and exhaust.

If you do go for the 3.4L package you would probably be better off going with some larger headers instead of the SSIs. They'll give you more top end and will help offset the cost of the 98mm P+Cs when compared with the price of the SSIs.

I guess it really comes down to intended use for the car and it's long term plans.

P.S. If it were me I would port the heads to Carrera spec 40I 38E or find a set of Carrera heads to swap out and buy a used 3.2 induction, harness and brain. Then install 1 5/8" headers

[rdane]

I built a similar CIS 3.4 on a '79 case. (98s and 74.4 crank) Drove it on the track, on a few hill climbs and lots of fun runs locally for a year. Sweet spot on that engien is 4 to 6K with 250#s of torque. Then I got the dumb (in retrospect) idea I needed a 3.6.

IMO the 3.4 was WAAYYYY more fun than my '95 3.6. Just make sure you match up the 3.4 engine to a short gear box and you'll be very happy in the end. The 3.4 is an awesome engine!

[Mysterytrain]

My 78SC engine came back to life as a 3.2 short stroke with 964 cams, CIS SSI's and a Dansk 2 in/1 out. Its been great..but its a street car and I was concerned with dealing with NJ state smog testing so I didn't do anything too wild. Like the others have said, it really depends what you plan to do with the car.

[bigchillcar]

dane..sounds like you're missing your 3.4. regrets?
ryan

[Michel J]

rdane, What happened to your 3.4?

Michel

[rdane]

I regret the loss of streeet car fun with the 3.4. The torque curve was amazing compared to the bit more powerful, but not as easily usable on the street, '95 3.6. I dropped another 250# off my car and thought the 3.6 would make a big perfiormance difference over the 3.4. It did not

Up side of the 3.6 is that it is a modern engine, modern engine managment, twin plugged and great gas milage (30+mpg on trips), etc. No quetsion the 3.6s are better engines but just not as fun IMO.

The 3.4 ended up with one of the local racers. He added big PMOs and my electromotive twin plug system. I suspect at that point he also pulled the 20/21 cams as well and put insomething to take advantage of the original build.

[Michel J]

Looks like I better start saving now. My goal is to have this 3.4 up and running by end of summer. I move slow(ask my neighbour) but I'm steady. Good thing I have time on my hands. Thanks

Michel